Authorities are nowsaying the explosive devices used in the Boston attack were fashioned from pressure cookers. Yes, like the kitchen pot you might use to cook rice at home. As it happens, pressure cookers have a nefarious reputation in counterterrorism circles. In 2004, the Department of Homeland Security (DHS) was concerned enough about pressure-cooker bombs to issue an alert to federal and state security officials: “A technique commonly taught in Afghan terrorist training camps is the use/conversion of pressure cookers into [improvised explosive devices],” the bulletin warned.

That bulletin cited several plots from 2002 to 2004 to use pressure-cooker bombs in France, India and Nepal. But more recently there have been at least three other instances of would-be terrorists in the West, all of them Islamic radicals, in possession of pressure cookers for reasons that seemed not to involve having friends over for dinner. One was an Army private linked to the 2009 Fort Hood shooter Nidal Hasan, who had reportedly been taking bombmaking tips from al-Qaeda’s short-lived (literally) online magazine Inspire and had various weapons and explosives along with his cooking pot. (The magazine reportedly recommended pressure cookers as explosive devices.) A 2010 suicide bomber in Stockholm had rigged a pressure-cooker bomb that failed to detonate. And as a newer DHS warning about the kitchen devices noted, the failed 2010 SUV bomb in New York’s Times Square was a pressure-cooker device containing 120 firecrackers. The same DHS memo refers to a March 2010 bombing with a pressure cooker at a Western Christian aid agency in Pakistan that killed six people.

Counterterrorism officials are surely well aware of these facts and studying any related leads. But it’s important to bear in mind that the ability to make these bombs is hardly unique to al-Qaeda and its sympathizers. Members of at least one prominent white-supremacist website have shared terrorist tips from Inspire, which one called “highly recommended reading.” Pressure-cooker bombs are also discussed in detail on this anarchist site, which describes how to build what is “affectionately known as a HELLHOUND.”

Nor do these devices require much money or special training. As DHS put it in 2004:

Typically, these bombs are made by placing TNT or other explosives in a pressure cooker and attaching a blasting cap at the top of the pressure cooker. The size of the blast depends on the size of the pressure cooker and the amount of explosive placed inside.

Pressure-cooker bombs are made with readily available materials and can be as simple or as complex as the builder decides. These types of devices can be initiated using simple electronic components including, but not limited to, digital watches, garage-door openers, cell phones or pagers. As a common cooking utensil, the pressure cooker is often overlooked when searching vehicles, residences or merchandise crossing the U.S. borders

The identity of the Boston bomber or bombers remains very much unclear, and it would be foolish to jump to conclusions. It would also be foolish to ignore the twisted recent history of the pressure cooker as a method for killing innocent people.